1. Facts, Factors and Inheritance
BLOOD
Facts, Factors and Inheritance

2. Blood Composition 55% of the blood consists of plasma
45% consists of formed elements
44% of the formed elements consist of erythrocytes
1% consists of leukocytes and platelets which is also called the buffy coat
plasma
buffy coat
erythrocytes

3. plasma The liquid component of blood
90% of the plasma is made up of water
8% is made up of proteins
2% is made up of several ions

4. Blood cells
Erythrocytes: red blood cells; function to transport oxygen
Leukocytes: white blood cells; function to protect the body
Platelets: cell fragments that function to clot the blood

5. Blood factors
Blood cells, like other cells in the body, have proteins or factors located on their surfaces
These factors can be antigens, substances that can cause the immune system to respond
There are 3 important blood factors used to type a person’s blood:
The ABO System
The MNS System
The Rh Factor

6. ABO System
In the ABO system there are two different blood proteins: A and B
The inheritance of these factors is based on codominance of the A and B proteins
In codominance, both alleles (different forms of a gene) in the heterozygote express themselves fully
There are 3 different blood alleles:
The A and B genes are both dominant
The o gene is recessive

7. Abo system (cont.) AA Ao BB Bo AB oo
Based on the 3 genes there are 4 possible phenotypes:
Type A blood
Type B blood
Type AB blood
Type O blood
There are 6 possible genotypes:
Possible Genotypes AA Ao BB Bo AB oo
Blood Types
Type A
Type B
Type AB
Type O

8. Abo system (cont.) A o B AB Bo o Ao oo
The inheritance of the ABO system can be predicted using Punnett squares
EX: A woman who is heterozygous for Type A blood has a child with a man who is heterozygous for Type B blood. What are the possible genotypes and phenotypes of their child? A o
Genotypes: AB, Bo, Ao, oo B AB Bo
Phenotypes: Type AB, Type B,
Type A, Type O o Ao oo

9. Abo system (cont.)
This system is important not only in forensics but in the medical field
It is important for blood transfusions
It is essential that the ABO blood types match to prevent the blood from clumping

10. ABO system (cont.) Type A Blood: Has A antigens and anti-B antibodies
If this person receives type B or type AB blood, the blood will clump as the anti-B antibodies attack the B antigens
Can receive type A and type O blood
Makes up 40% of the population

11. ABO system (cont.) Type B Blood: Has B antigens and anti-A antibodies
If this person receives type A or type AB blood, the blood will clump
Can receive type B and type O blood
Makes up 11% of the population

12. ABO system (cont.) Type AB Blood:
Has A and B antigens and no ABO antibodies
Because this person doesn’t have ABO antibodies, they can receive any type blood, making this person the universal recipient
Makes up 4% of the population

13. ABO system (cont.) Type O Blood:
Has no antigens and anti-A and anti-B antibodies
Because this person doesn’t have antigens, they can donate to any type blood, making this person the universal donor
Can only receive type O blood
Makes up 45% of the population

14. Mns system Similar to the ABO System
A person carries either the M protein, the N protein or the S protein on their blood cells
M is found in 30% of the population
N is found in 22% of the population
S is found in 48% of the population

15. Rh Factor The Rh protein can be found on the surface of the blood cell
Rh+: the person has the Rh antigen; it is found in 84% of the population
Rh-: the person does not have the Rh antigen; makes up 16% of the population
O+ 38 percent of population O- 7 percent of population
A+ 34 percent of population A- 6 percent of population
B+ 9 percent of population B- 2 percent of population
AB+ 3 percent of population AB- 1 percent of population

16. Calculating probabilities
Knowing the percentages of the population with the different blood factors can be used to determine the likelihood of a certain combination of blood factors
By multiplying the ratios of the types, you can determine the probability of having a certain blood type

17. Calculating probabilities (cont.)
EX: What is the probability of a person having blood type A and N and being Rh-?
A N Rh-
40% x 22% x 16% = ?
.40 x .22 x .16 = .01
1 out of every 100 people would have blood type A and N and be Rh-